Terminal method and manufacture

ABSTRACT

An end mill is used to form a reduced thickness step in an indefinite length of strip material. If, due to tolerances and other factors the reduced thickness material is slightly too thick, it is swaged to a reduced thickness following which terminals are formed of both the thinned and original thickness material.

United States Patent [1 1 Berg Sept. 18, 1973 22 Filed? TERMINAL METHODAND MANUFACTURE [75] inventor: Qilentin lierg,Cuml aerland, Pa.

[73] Assignee: m v

Company, Wilmington, Del.

[2]] Appl. No.: 220,307

Related US. Application Data [62] Division of Ser. No. 100,252, Dec. 2],1970, Pat. No.

[52] US. Cl 29/630, 29/203 D, 72/341, 72/404, 90/21 [51] Int. Cl H0lr9/00 [58] Field of Search 29/628, 629, 630 R,

29/630 A, 630 G, 203 D, 203 DT, 203 S; 72/404, 405, 341; 339/276 TWatanabe 339/258 3,494,253 l/l970 Hood et al 90/2l 2,600,190 6/l952Batcheller 173/363 Primary Examiner-Charles W. Lanham AssistantExaminer-James R. Duzan Att0rney-Thomas Hooker [57] ABSTRACT An end millis used to form a reduced thickness step in an indefinite length ofstrip material. if, due to tolerances and other factors the reducedthickness material is slightly too thick, it is swaged to a reducedthickness following which terminals are formed of both the thinned andoriginal thickness material.

11 Claims, 12 Drawing Figures PATENTEDSEPIBIQTB 3.758.944

SHEET 2 0f 3 PATENTEBSEPIBW 3.758.944

sum 3 0r 3 IIIII'I J TERMINAL METHOD AND MANUFACTURE This is a divisionof application Ser. No. l00,252 filed Dec. 2|, 1970, now U.S. Pat. No.3,707,933, granted Jun. 2, I973.

The invention relates particularly to the formation of crimp typeelectric terminals from an indefinite length of strip stock where it isrequired that different parts of the terminals be formed of metal ofdifferent thicknesses, with the thickness of the metal in at least onepart of the terminal strip maintained to a precise tolerance.

The terminals are formed by feeding uniform thickness strip stock past afixed end mill which is rotated to cut a reduced thickness step in thestrip. Following this stress relief windows are formed at intervalsalong the step. If the material between the windows is too thick it isthen swaged or stamped to the exact desired thickness. The materialdisplaced during the swaging step bulges into the adjacent windowsformed in the step and does not alter the thickness of the adjacentunmilled portion of the strip. By the use of this method the thicknessof the material located between the swaging tooling is controlled towithin 1 0.0003 inches of the desired thickness. A crimp type terminalis then formed, preferably by a stamping operation, from both thethinned material and a portion of the original thickness strip materialwith the crimp barrel of the terminal formed from the thinned material.The terminal may be secured to a carrier strip cut out of the step.

Large numbers of crimp type terminals are used in modern electronicapparatus such as computers where it is essential that the electricalproperties of each terminal be retained within a very close tolerancethroughout the useful life of the apparatus. An electronic computer mayutilize as many as l00,000 terminals each of which must functionproperly in order for the computer to function properly. If a singleterminal fails, the entire computer fails. It is essential that thecrimp type connections between the terminals and conductors in thecomputer have uniform low contact resistance throughout the life of thecomputer. Computers use solid state components, integrated circuits,memory frames and other circuit elements which are driveii by lowvoltage and amperage currents and accordingly are easily affected byslight changes in the contact resistance of a single crimp connection.

In order to achieve the uniformity of the crimp connection in each ofthe large number of terminals, the crimp barrel of each terminal must beformed from metal stock having an exact thickness so that when crimpedto the conductor a long lived low contact resistance crimp connection isformed. If the crimp barrel is formed of material too thin, thenthecrimping tooling will not form a tight low resistance connectionbetween the terminal and the conductor. If the thickness of the crimpmaterial is too great, there is a tendency for the crimp barrel torebound open following crimping. in either case the desired crimpconnection is not formed and it is likely that the contact resistance ofthe connection will increase during the life of the computer.

In certain types of computers and the like, it is desirable to use crimptype terminals where the disconnect portion of the terminal is formedfrom strip material having a greater thickness then the thickness of thematerial used to form the crimp barrels. The disconnect portions of theterminals may be formed from commer--' cially available strip stock ofuniform thickness. The difficulty arises in thinning the strip stock toprovide the required thinner material for the crimp barrels. The problemof providing the thin crimp barrel material is compounded by the factthat the terminals must he rapidly and inexpensively mass produced inlarge numbers yet must conform to the very stringent thickness tolerancein order to achieve the desired reliability of the crimp connections.

Hood et al, U.S. Pat. No. 3,494,253 discloses apparatus for forming astep in an indefinite length of strip material. It has been proposedthat the Hood apparatus be used for forming the reduced thickness crimpbarrel material in the manufacture of computer crimp terminals. The Hoodpatent utilizes a circumferential cutter for forming in a step in thestrip which is moved continuously past the cutter. The result is areduced thickness step having a scalloped surface due to the fact thateach individual cutting tooth on the cutter cuts one portion of thestrip as it is swept in a circular path, and the next cutter tooth cutsa different portion of the strip located slightly upstream of the firstportion, thus resulting in undesired variations in thickness of thestep.

Additionally the use of a circumferential cutter as taught by Hood etal. imparts differential stresses in the milled step which tend to causeterminal carrier strips fomted therefrom to twist or snake duringreeling and to jam when fed along the feed path of a tenninalapplicator. The teeth of a circumferential cutter dull sooner than thecutting teeth of an end mill so that the use of an end mill in formingthe reduced thickness step reduces down time necessitated when thecutting mills are changed and also reduces the frequency of adjustmentof the cutting tool relative to the strip.

Accordingly, an object of the invention is to provide a method andapparatus for forming crimp type electric terminals from strip stockmaterial in which the disconnect portion of the terminal is fonned fromthe strip stock and the crimp barrel is formed from a reduced thicknessportion of the strip stock. The thickness of the crimp barrel materialis held to a very close tolerance in order to assure minimum contactresistance at the crimp connection.

Another object is to provide a method and apparatus for reducing thethickness of a strip of metal of indefinite length.

A further object of the invention is to provide electric terminalsformed from differential thickness strip material. The terminals may besecured together on a carrier strip of indefinite length. The strip isnot stressed so that reeling and feeding of the strip in an applicatoris facilitated and snaking and binding are reduced.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings of which these are three sheets.

IN THE DRAWINGS H6. 1 is a partially broken away side view ofapparawidth and depth to permit the strip FIG. 6 is an enlarged view ofthe cutting end of the end mill illustrated in FIG. 1;

FIG. 7 is a view illustrating performed on the milled strip terminalstherefrom;

FIG. 8 is a sectional view of the tooling used to perform one of thesteps of forming the strip;

FIG. 9 is a partially broken away view of a modified milling apparatus;

FIG. 10 is a partially broken away view of the miller of FIG. 9;

FIG. 11 is a view of a strip with a different step milled therein; and

FIG. 12 is a view similar to part of FIG. 7 illustrating the manufactureof terminals from the strip of FIG. 11.

As illustrated in FIG. 1, a flat metal strip 10 of indefinite length isfed through a milling apparatus 12 by strip feed 14. The feed 14comprises a pair of feed rollers 16 and 18 which are rotated in thedirection of arrows 20 by suitable drive means 22. One of the rollersmay be resilient so that the strip 10 is frictionally engaged betweenthe rollers and rotation of the rollers moves the strip in the directionof arrow 24 past the miller.

The miller 12 includes a base block 26 mounted on support 28 and havinga flat strip feed groove 30 formed therein. A cover plate 32 rests onthe top of the block 26 and is secured thereto so as to confine thestrip 10 in the groove 30. The groove has sufficient to be pulled freelythrough the miller. End mill 34 is mounted in suitable drive means (notshown) with the cutting end of the mill projecting down through anopening 36 in cover plate 32. The rotational axis of the end mill isperpendicular to the longitudinal axis of the groove 30 and of strip 10as the strip is moved past the mill. Cutting edges 40 of the mill teeth42 (see FIG. 6) are spaced above the bottom of strip feed groove 30 adistance less than the thickness of the strip 10. As indicated in FIGS.1 and 2, mill 34 is rotated in the direction of arrows 44. Rotation ofthe end mill cuts away a portion of the strip 10 to form a reducedthickness step 46 on one side of the strip. The diameter of the end millis somewhat greater than the width of the step 46 so that each cuttingedge 40 of the mill sweeps over strip edge 48 to assure that a smoothcorner is obtained.

Bevels 50 are provided at the outer edges of the end mill cutting teeth42 so that, as illustrated in FIG. 3, the mill cuts out a slantedsurface 52 between the step 46 and the top of the strip 54.

The milling apparatus 12 illustrated in the drawings may be providedwith means for cooling the end mill and for removing chips from the workarea. These means are conventional and form no part of the invention.

During the milling operation, feed 14 moves strip 10 through the millingapparatus 12 at a uniform rate of speed and the end mill is rotated at arelatively high rotational speed in order to mill the step 46. Most ofthe material removed from the step is cut away during the period of timewhen each cutter 42 sweeps past the upstream arcuate edge 56 of the step46. Each sweep of a tooth 42 past edge 56 removes a chip of stripmaterial. During the completion of each revolution of end mill 34, thetooth 42 sweeps over the step 46. Because of the practical difficultiesin maintaining the end mill axis 38 exactly'perpendicular to thelongitudinal axis of the strip 10, and in maintaining the feed groove 30so the manufacturing steps during the formation of that the bottomsurface thereof is perfectly flat, the teeth 42 engage the strip 10during the entirety of each revolution of the tool 34 with the exceptionof the time when they are to one side of strip edge 48. The patternformed in the step 46 by this type of milling is illustrated in FIG. 4.In contrast to the use of a circumferential cutting tool for formingstrips as disclosed in Hood et al. U.S. Pat. No. 3,494,253, the use ofan end mill to form a step in strip 10 as disclosed does not imparttwisting stress to the thinned portion of the strip. This is because thestresses from the milling operation are distributed relatively uniformlythroughout the step.

Milling of the step is performed by cutting away material both againstthe direction in which the strip is moved past the mill, and also in thedirection the strip is moved past the mill. Thus, the milling operationtends not to affect the strip feed and the strip is moved uniformly pastthe mill.

Each of the cutting teeth 42 sweeps over the entire surface of the step46 so that the thickness of the step is uniform despite the fact thatone or more of the teeth 42 may project toward the strip a distanceslightly greater than the remaining teeth. Each of the teeth 42 performsessentially the same amount of work and cuts virtually idential chipsfrom the upstream step edge 56 during each sweep past the edge. Thisfeature extends the useful life of the end mill. As indicated in FIG. 5,the uniform movement of the strip 10 past the end mill 34 forms crestsand valleys in the slanted step edge 52.

The portion of the strip downstream from strip feed 14 may be wound on areel for storage. Subsequently the strip is unwound from the reel andfed to a punch press used to fonn the individual crimp terminals.

When a sharp end mill is installed in the milling apparatus 12, theaxial height of the end of the mill above the strip feed path 30 isadjusted to 0.0122 inches. During the milling of an entire strip 10,which may have a length of from 800 to 1,000 feet, a certain amount ofwear occurs in the end mill. This wear may be as much as 0.0005 inchesper strip so that the step which is milled from the upstream part of thestrip will be slightly thicker than the step at the downstream end ofthe strip. Additionally, the step material may be thicker thancontemplated due to differences in the hardness and toughness of themetal at different locations in the strip itself. The result of thesevariations and miller wear is that the milling operation forms a stepalong the entire length of the strip which is at no point thinner than0.0122 inches but which may be 0.0l30 inches thick or thicker at someplaces. The strip tends to be somewhat thinner at the downstream than atthe upstream end.

FIG. 7 illustrates generally from left to right the steps used to form acrimp type electrical terminal 60 from the stepped strip lotThe terminal60 includes a disconnect portion 62 and a crimp portion 64. Thedisconnect portion is formed from the original thickness of portion 66of the strip and the crimp portion is formed from the reduced thicknessstep portion 46. The strip 10 may be formed of phos-bronze in order thatthe terminal 60 has the desired electrical and mechanical properties.

Typically the manufacturing tolerances for the terminal 60 require thatthe thickness of the metal used to form the crimp portion 64 of terminal60 is less than the thickness of the metal used to form the disconnectportion 62. The thickness of each portion must be maintained within anexact tolerance. The thickness tolerance of the metal used to form thecrimp portion 64 is assured by milling the step 46 as described and byforming the disconnect portion from the step metal in the manner to bedescribed.

In forming terminals from the bi-level strip, the strip is fed from thesupply reel through a punch assembly (not illustrated) in the directionof arrow 68 in FIG. 7. The press assembly includes a number of pressstations each of which performs an operation on a portion of the strip.These operations will be described in the sequence of operation.

The first operation performed on the strip is to punch out a pilot hole70 and a swage relief window or opening 72 from the step. The opening 72extends laterally across the step 46 and is located to one side of thematerial 74 used to form the terminal crimp portion 64.

As previously described, the thickness of the milled step may vary froma minimum thickness of 0.0122 inches to a thickness of 0.0130 inches ormore depending upon the wear on the end mill and the physical propertiesof the strip itself. This variation in thickness is too great to assureuniform crimp connections for the useful life of the computer orapparatus in which the terminal is used. The minimum thickness of 0.0122inches is alright, however the step may be too thick.

In order to assure that the thickness of the step material 74 which isused to form the terminal crimp portion 64 is not greater that themaximum tolerance, the material is passed beneath a flat swaging die 76after the formation of openings 72. The strip 10 is confined in a feedpath 78 formed in the support 80 beneath the die 76. The die 76 bottomsto a clearance of 0.0128 inches above the bottom of the feed path 78 sothat it will reduce the thickness of the step portion 74 to 0.0128inches if the thickness of the material when milled was greater than0.0128 inches. During the swaging operation, as illustrated in FIG. 8,the material which is displaced bulges outwardly into the openings orwindows 72 to either side of the step portion 74 so that the swagingstep does not distort the original thickness material 66 used to formthe disconnect portion 62.

In FIG. 7, the thickness of the step material 74 is greater than 0.0128inches so that when the tool 76 bottoms it engages the strip to flattenportion 73 where indicated. If the thickness of the milled step 46 isless than 0.0128 inches the tool 76 when bottomed does not engage thestep and the step would not carry the swaging marks. In any event, theswaging operation as described assures that the final thickness of theportion 74 of the step 46 used to form the terminal crimp portion 64 is0.0125 i 0.0003 inches, which is within the required thickness standardsfor the formation of reliable crimp connections.

During the swaging operation illustrated in FIG. 8 the bevelled corner84 of tool 76 engages the undulating surface 52 to flatten the same.Surface 52 is flattened whether or not bottoming of the tool 76 reducesthe thickness of the step portion 74.

After the swaging operation is performed, the terminal disconnectportion 62 is cut out of the strip portion 66 in a number of steps.Following this the crimp barrel portion 64 is stamped from the swagedpart 74 of the step 46 as illustrated. Wire crimp barrel 86 is formedentirely from the swaged portion of step 46 while the outer tips of theinsulation crimp barrel 88 extend beyond the swaged portion of the step.Prior to the forming of the wire and insulation crimp barrels 86 and 88,

dimples 90 may be formed in crimp portion 64. The dimples improve thecrimp connections.

As illustrated, the terminals 60 formed from the strip 10 project to oneside from a carrier strip 92 which is formed from the step 46. Themilling operation used to reduce the thickness of this portion of thestep equalizes the cutting stresses along the strip 92 so that the stripdoes not tend to twist or snake during winding of the terminals andstrip on a supply reel or during feeding of the strip in an applicator.The use of a circumferential mill to form steps in strip stock inaccordance with the teaching of the prior art Hood et al. US. Pat. No.3,494,253, produced unequal stresses in the carrier strip formedtherefrom with the result that the terminal strip tends to twist, snakeand tangle. Use of the dis closed milling techniques reduces theseproblems.

Crimp barrel 86 is spaced from disconnect portion 62 by a flat neck 94of the sized step material 74. The thickness of neck 94 may be checkedby a suitable instrument to assure that the thickness of the crimpbarrel 86 is within the tolerance required to form a reliable crimpconnection.

FIGS. 9 and I0 illustrate a different embodiment of the millingapparatus 12 of FIGS. '1 and 2. The milling apparatus of FIGS. 9 and 10is identical to miller 12 with the exception that the strip 102, whichis pulled through the miller by a feed like feed 14, is firmly heldagainst the bottom of feed path 104 by three spring backed clamps 106,108 and 110. The clamps are mounted in the top plate 112 of the millingapparatus. Clamp 106 extends nearly across the entire width of the strip102 immediately upstream of the end mill 114 which is used to cut step116 in the strip. The clamp 108 is located laterally to one side of theend mill 114 and clamp is located immediately downstream of the end milland engages the reduced thickness step 116.

The three clamps assure that the portion of the strip which is milled isheld against the bottom of the feed path 104 thereby preventing anylifting or chatter of the strip which could occur as a result of themilling operation. For instance, the tendency for the individual cutterblades of the end mill to lift the strip from the feed path duringcutting is eliminated. In this way the minimum step thickness is furtherassured. In other respects the milling apparatus 100 is identical toapparatus 12.

FIG. 11 illustrates a modification of the invention according to which areduced thickness step 118 is formed within the width of strip 120. Step118 may be formed by the use of a milling apparatus as illustrated ineither FIGS. 1 or 9 in which a small diameter end mill is used and wherethe end mill is located so that it does not sweep over the edge of thestrip.

FIG. 12 illustrates terminals 122 which may be formed from the strip 120in the same way as indicated in FIG. 7. The terminals 122 are secured toa carrier strip 124 which in this case is formed from an originalthickness portion of the strip 120 as opposed to the carrier strip 92 ofFIG. 7 which is formed from the reduced.

thickness step material. The terminals 122 are identical to terminals60.

While the inventions disclosed herein are particularly useful in themanufacture of electric terminals, it is not intended that they belimited solely to this art since the manufacture of stepped stripmaterial of indefinite length to precise tolerances may be useful inapplications which do not relate to terminals. Likewise, it is notintended that the invention be related to the manufacture of electricterminals of the particular type disclosed. Obviously terminals may bemanufactured in accordance with the invention which utilize a disconnectportion of a type different than that disclosed in terminal 60.

While I have illustrated and described preferred embodiments of myinvention, it is understood that these are capable of modification, andI therefore do not wish to be limited to the precise details set forth,but desire to avail myself of such changes and alterations as fallwithin the purview of the following claims.

What I claim as my invention is:

l. The method of forming crimp type terminals from a strip of metal ofindefinite length comprising the steps of:

1. Reducing the thickness of at least a part of the strip by moving thestrip between the end of a rotating end mill and a strip support spacedaway from the end of the mill a distance less than the thickness of thestrip;

2. Forming stress relief windows at periodic intervals along the lengthof the reduced thickness part of the strip;

3. Swaging any reduced thickness parts of the strip between adjacentwindows having a thickness greater than a maximum thickness down to auniform maximum thickness; and

4. Forming terminals from the strip at period intervals therealong witheach terminal including both a wire crimp barrel formed from a part ofthe strip between adjacent windows and a disconnect portion.

2. The method of Claim l including the steps of milling a reducedthickness step in the strip while retaining an original thicknessportion of the strip, and forming the disconnect terminal portions fromoriginal thickness strip material.

3. The method of Claim 2 including the steps of forming the reducedthickness step at one edge of the strip, punching the terminals from thestrip and providing a terminal carrier strip from the reduced thicknessstep with each terminal secured to the carrier strip.

4. The method ofclaim 1 including the step ofclamping the strip againstthe strip support adjacent the end mill as the strip is moved past theend mill.

5. The method of claim 1 including the step of biasing the strip againstthe strip support immediately upstream and immediately downstream of theend mill as the strip is moved past the end mill.

6. The method of claim 5 including the step of biasing the reducedthickness part of the strip against the strip support immediatelydownstream of the end mill.

7. The method of claim 1 including the steps of forming a reducedthickness step at one edge of the strip with an original thicknessportion of the strip at the other edge thereof and biasing the stripagainst the strip support immediately upstream of the end mill, biasingthe original thickness portion of the strip to one side of the end millagainst the strip support and biasing the reduced thickness portion ofthe strip immediately adjacent the end mill against the strip supportwhile moving the strip past the end mill.

8. The method of forming a crimp type terminal from a strip of metal ofindefinite length comprising the steps of:

1. Reducing the thickness of at least a part of the strip along theentire length thereof to form a thin strip;

2. Reducing the thickness of portions of the thin strip which arethicker than a maximum tolerance to assure a uniform maximum thicknessof the thin strip; and

3. Forming crimp type electrical terminals from the strip with eachterminal including a crimp barrel formed from said thin strip.

9. The method of claim 8 including the step of ex panding the metaldisplaced during reducing the thickness of portions of the thin stripinto openings in the thin strip.

10. The method of claim 8 including the step of forming a terminalcarrier strip from the thin strip.

ill. The method of claim 10 including forming a disconnect part of eachterminal from an original thickness portion of the strip.

i t i

1. The method of forming crimp type terminals from a strip of metal ofindefinite length comprising the steps of:
 1. Reducing the thickness ofat least a part of the strip by moving the strip between the end of arotating end mill and a strip support spaced away from the end of themill a distance less than the thickness of the strip;
 2. Forming stressrelief windows at periodic intervals along the length of the reducedthickness part of the strip;
 2. The method of Claim 1 including thesteps of milling a reduced thickness step in the strip while retainingan original thickness portion of the strip, and forming the disconnectterminal portions from original thickness strip material.
 2. Reducingthe thickness of portions of the thin strip which are thicker than amaximum tolerance to assure a uniform maximum thickness of the thinstrip; and
 2. Forming stress relief windows at periodic intervals alongthe length of the reduced thickness part of the strip;
 3. Swaging anyreduced thickness parts of the strip between adjacent windows having athickness greater than a maximum thickness down to a uniform maximumthickness; and
 3. Forming crimp type electrical terminals from the stripwith each terminal including a crimp barrel formed from said thin strip.3. The method of Claim 2 including the steps of forming the reducedthickness step at one edge of the strip, punching the terminals from thestrip and providing a terminal carrier strip from the reduced thicknessstep with each terminal secured to the carrier strip.
 3. Swaging anyreduced thickness parts of the strip between adjacent windows having athickness greater than a maximum thickness down to a uniform maximumthickness; and
 4. Forming terminals from the strip at period intervalstherealong with each terminal including both a wire crimp barrel formedfrom a part of the strip between adjacent windows and a disconnectportion.
 4. The method of claim 1 including the step of clamping thestrip against the strip support adjacent the end mill as the strip ismoved past the end mill.
 4. Forming terminals from the strip at periodintervals therealong with each terminal including both a wire crimpbarrel formed from a part of the strip between adjacent windows and adisconnect portion.
 5. The method of claim 1 including the step ofbiasing the strip against the strip support immediately upstream andimmediately downstream of the end mill as the strip is moved past theend mill.
 6. The method of claim 5 including the step of biasing thereduced thickness part of the strip against the strip supportimmediately downstream of the end mill.
 7. The method of claim 1including the steps of forming a reduced thickness step at one edge ofthe strip with an original thickness portion of the strip at the otheredge thereof and biasing the strip against the strip support immediatelyupstream of the end mill, biasing the original thickness portion of thestrip to one side of the end mill against the strip support and biasingthe reduced thickness portion of the strip immediately adjacent the endmill against the strip support while moving the strip past the end mill.8. The method of forming a crimp type terminal from a strip of metal ofindefinite length comprising the steps of:
 9. The method of claim 8including the step of expanding the metal displaced during reducing thethickness of portions of the thin strip into openings in the thin strip.10. The method of claim 8 including the step of forming a terminalcarrier strip from the thin strip.
 11. The method of claim 10 includingforming a disconnect part of each terminal from an original thicknessportion of the strip.